RELATED APPLICATIONS
FIELD OF THE INVENTION
[0002] The present application relates to multi-dose medication injection pen devices with
improved functionality, including improved dial-back of a set dose, and improved last
dose control.
BACKGROUND OF THE INVENTION
[0003] Various medication injection pen devices are known in the prior art. These prior
art devices sometimes include features for enabling a user to correct a dose that
has been set too large, which may be referred to as "dial back". Another feature that
may be provided by some of the prior art devices is the ability to control a last
dose of a medication cartridge such that a user cannot set a dose greater than the
remaining amount of medication in the cartridge. This feature is referred to as last
dose control or last dose management. Both of these features are desired by users
of such pen devices; however, the prior art devices do not satisfactorily meet these
needs. Many prior art devices may provide one of these features, but not both. Further,
many of the prior art devices require additional steps for performing dial back, which
are cumbersome and not intuitive to the user. Thus, there is a need in the art to
provide improved functionality of dial back and last dose control mechanisms together
in a medication injection pen.
SUMMARY OF EMBODIMENTS OF THE INVENTION
[0004] Exemplary embodiments of the present invention address at least the above problems
and/or disadvantages and provide at least the advantages described below.
[0005] Accordingly, a first exemplary embodiment of the present invention provides a medication
injection pen comprising a housing, for housing a dose set knob, a leadscrew, a driver,
a setback member, and a dose stop member. The dose set knob is rotatable with respect
to said housing to set a desired injection dose, and comprises at least one internal
thread. The leadscrew includes a thread element by which it is advanceable in a first
direction via a corresponding thread engagement, said first direction being that which
expels medication from a cartridge. The driver is rotationally fixed to said leadscrew
for preventing relative rotation therebetween, said driver being rotatable in a first
direction to rotate and advance said leadscrew in said first direction. The setback
member is rotationally fixed to said driver for preventing relative rotation therebetween.
The dose stop member is rotationally fixed to said setback member and comprises an
external thread in threaded engagement with said internal thread of said dose set
knob, said dose stop member being axially movable relative to said dose set knob when
said dose set knob is rotated relative to said setback member, and wherein axial movement
of said dose stop member limits the user from setting a dose that is greater than
an injectable volume of medication remaining in the cartridge.
[0006] According to another exemplary embodiment of the present invention a medication injection
pen is provided comprising a housing, for housing a dose set knob, a leadscrew, a
driver, a setback member, and a dose stop member. The dose set knob is rotatable with
respect to said housing to set a desired injection dose. The leadscrew includes a
thread element by which it is advanceable in a first direction via a corresponding
thread engagement, said first direction being that which expels medication from a
cartridge. The driver is rotationally fixed to said leadscrew for preventing relative
rotation therebetween, said driver being rotatable in a first direction to rotate
and advance said leadscrew in said first direction. The setback member is rotationally
fixed to said driver for preventing relative rotation therebetween, and is provided
with an external thread thereon. The dose stop member is rotationally fixed to said
dose set knob and comprises an internal thread in threaded engagement with said external
thread of said setback member, said dose stop member being axially movable relative
to said dose set knob when said dose set knob is rotated relative to said setback
member, and wherein axial movement of said dose stop member limits a user from setting
a dose that is greater than an injectable volume of medication remaining in the cartridge.
[0007] According to yet another exemplary embodiment of the present invention a medication
injection pen is provided comprising a housing, for housing a dose set knob, a leadscrew,
a driver, a setback member, and a dose stop member. The dose set knob is rotatable
with respect to said housing to set a desired injection dose. The leadscrew includes
a thread element by which it is advanceable in a first direction via a corresponding
thread engagement, said first direction being that which expels medication from a
cartridge. The driver is rotationally fixed to said leadscrew for preventing relative
rotation therebetween, said driver being rotatable in a first direction to rotate
and advance said leadscrew in said first direction. The setback member is rotationally
fixed to said driver for preventing relative rotation therebetween. The dose stop
member is rotationally fixed to said dose set knob and comprises an internal thread
in threaded engagement with said thread of said leadscrew, said dose stop member being
axially movable relative to said dose set knob when said dose set knob is rotated
relative to said setback member, and wherein axial movement of said dose stop member
limits a user from setting a dose that is greater than an injectable volume of medication
remaining in the cartridge.
[0008] According to yet another exemplary embodiment of the present invention a medication
injection pen is provided comprising a housing, for housing a dose set knob, a leadscrew,
a driver, a setback member, and a click element. The dose set knob is rotatable with
respect to said housing to set a desired injection dose. The leadscrew includes a
thread element by which it is advanceable in a first direction via a corresponding
thread engagement, said first direction being that which expels medication from a
cartridge. The driver is rotationally fixed to said leadscrew for preventing relative
rotation therebetween, said driver being rotatable in a first direction to rotate
and advance said leadscrew in said first direction. The setback member is rotationally
fixed to said driver for preventing relative rotation therebetween. The click element
is positioned between said dose set knob and said setback member, said click element
comprising a first arm member engaging an internal surface of said dose set knob,
and a second arm member engaging an external surface of said setback member, wherein
one of the said first and second arms produces an audible signal when said dose set
knob is rotated with respect to said housing.
[0009] According to yet another exemplary embodiment of the present invention a medication
injection pen is provided comprising a housing, for housing a dose set knob, a leadscrew,
a driver, and a setback member. The dose set knob is rotatable with respect to said
housing to set a desired injection dose. The leadscrew includes a thread element by
which it is advanceable in a first direction via a corresponding thread engagement,
said first direction being that which expels medication from a cartridge. The driver
is rotationally fixed to said leadscrew for preventing relative rotation therebetween,
said driver being rotatable in a first direction to rotate and advance said leadscrew
in said first direction. The setback member is rotationally fixed to said driver for
preventing relative rotation therebetween. The housing further comprises a flexible
protrusion provided on a surface within said housing, and the dose set knob further
comprises a flexible tab element which engages said protrusion to produce an audible
signal upon completion of injection of a set dose.
[0010] Additional objects, advantages and salient features of exemplary embodiments of the
invention will become apparent to those skilled in the art from the following detailed
description, which, taken in conjunction with annexed drawings, discloses exemplary
embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The above and other exemplary features and advantages of certain exemplary embodiments
of the present invention will become more apparent from the following description
of certain exemplary embodiments thereof when taken in conjunction with the accompanying
drawings, in which:
Fig. 1 depicts a medication injection pen according to an exemplary embodiment of
the present invention;
Figs. 2A and 2B depict unassembled and assembled cross-sectional views, respectively,
of exemplary components provided in a medication injection pen according to a first
exemplary embodiment of the present invention;
Fig. 2C depicts an unassembled view of a pen needle usable in exemplary embodiments
of the present invention;
Figs. 3A and 3B depict views of a body provided in a medication injection pen according
to the first exemplary embodiment of the present invention;
Figs. 4A and 4B depict views of a dose set knob provided in a medication injection
pen according to the first exemplary embodiment of the present invention;
Figs. 5A and 5B depict views of a setback member provided in a medication injection
pen according to the first exemplary embodiment of the present invention;
Figs. 6A and 6B depict views of a click element provided in a medication injection
pen according to the first exemplary embodiment of the present invention;
Fig. 7 depicts a view of a driver and leadscrew arrangement provided in a medication
injection pen according to the first exemplary embodiment of the present invention;
Figs. 8A and 8B depict views of a dose stop member provided in a medication injection
pen according to the first exemplary embodiment of the present invention;
Figs. 9A and 9B depict views of a leadscrew brake provided in a medication injection
pen according to the first exemplary embodiment of the present invention;
Figs. 10A and 10B depict views of an alternative injection coupling mechanism provided
in a medication injection pen according to the first exemplary embodiment of the present
invention;
Figs. 11A - 11F depict views of alternative leadscrew brake and threaded insert embodiments
provided in a medication injection pen according to the first exemplary embodiment
of the present invention;
Figs. 12A - 12E depict views of an end-of-injection click mechanism in a medication
injection pen according to the first exemplary embodiment of the present invention;
Fig. 13 depicts a view of a muted injection click mechanism in a medication injection
pen according to the first exemplary embodiment of the present invention;
Figs. 14A and 14B depict views of an additional mechanism for reducing friction between
components in a medication injection pen according to the first exemplary embodiment
of the present invention;
Figs. 15A and 15B depict exemplary mechanisms for connecting a cartridge to a medication
injection pen according to the first exemplary embodiment of the present invention;
Figs. 16A and 16B depict unassembled and assembled cross-sectional views, respectively,
of exemplary components provided in a medication injection pen according to a second
exemplary embodiment of the present invention;
Fig. 17 depicts a view of a driver and leadscrew arrangement provided in a medication
injection pen according to the second exemplary embodiment of the present invention;
Fig. 18 depicts a view of a last dose control mechanism provided in a medication injection
pen according to the second exemplary embodiment of the present invention;
Figs. 19A and 19B depict views of alternative last dose control mechanisms provided
in a medication injection pen according to the second exemplary embodiment of the
present invention;
Fig. 20 depicts an assembled cross-sectional view of exemplary components provided
in a medication injection pen according to a third exemplary embodiment of the present
invention;
Fig. 21 depicts a view of a body provided in a medication injection pen according
to the third exemplary embodiment of the present invention;
Fig. 22 depicts a view of an insert provided in a medication injection pen according
to the third exemplary embodiment of the present invention;
Fig. 23 depicts a view of a driver provided in a medication injection pen according
to the third exemplary embodiment of the present invention;
Fig. 24 depicts a view of a dose set knob provided in a medication injection pen according
to the third exemplary embodiment of the present invention; and
Fig. 25 depicts a view of a setback member provided in a medication injection pen
according to the third exemplary embodiment of the present invention.
[0012] Throughout the drawings, like reference numerals will be understood to refer to like
elements, features and structures.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0013] The matters exemplified in this description are provided to assist in a comprehensive
understanding of exemplary embodiments of the present disclosure with reference to
the accompanying drawing figures. Accordingly, those of ordinary skill in the art
will recognize that various changes to and modifications of the exemplary embodiments
described herein can be made without departing from the scope and spirit of the claimed
invention. Also, descriptions of well-known functions and constructions are omitted
for clarity and conciseness.
[0014] With reference to the drawing figures, particularly FIG. 1, a medication injection
pen is shown and generally designated with the reference numeral 10. The medication
injection pen 10 may be used for the administration of various medications, preferably
liquid in nature, including but not limited to insulin and human growth hormone. The
term "medication" is used in an illustrative and non-limiting manner to refer to any
substance that may be injected into a patient for any purpose. The medication injection
pen 10 is provided for administering multiple injections, the dose or volume of which
may be set by the user and may vary for each injection. Exemplary embodiments of medication
injection pen 10 of the present disclosure may be either disposable or reusable when
the supply of medication therein has been exhausted.
[0015] With reference to FIGs. 2A and 2B, in an exemplary embodiment, the medication injection
pen 10 generally includes a cap 12, a cartridge holder 14, a spinner 16, a body 18,
a dose knob 20, a setback member 22, a driver member 24, a leadscrew 26, a dose stop
member 28, a bi-directional click element 30, a leadscrew brake 32, and a push button
34.
[0016] The cartridge holder 14 is formed to accommodate a medication cartridge 36, which
may be of any conventional design. By way of non-limiting example, the cartridge 36
may include an elastomeric septum 38 at a distal end thereof, and an open proximal
end 37 which exposes a slidable plunger 40. A medication is contained within the cartridge
36 between the septum 38 and the plunger 40. As will be described in more detail below,
the spinner 16 is configured to engage the plunger 40 and force a distal movement
thereof to expel the medication from the cartridge 36. The spinner 16 includes an
aperture formed to snap fit or otherwise engage a distal end bead portion 27 (FIG.
7) of leadscrew 26 in mounting the spinner 16 onto the leadscrew 26. A standard pen
needle 11 (FIG. 2C) is used to administer medication from the medication injection
pen 10. The needle is a double-ended cannula 5 which is threadedly mounted onto threads
42 of the cartridge holder 14, as is well known in the art. One end of the cannula
5 is exposed for insertion into a patient, while the second end of the cannula is
disposed to pierce the septum 38 of the cartridge 36. After administration of a set
dose, the needle 11 may be removed, in which case, the septum 38 may be self-sealing.
The cap 12 is formed to releasably mount onto the cartridge holder 14, such as with
a snap fit or other releasable engagement, to limit contamination of the septum 38
and the surrounding portions of the cartridge holder 14. A resilient holding arm 13
may extend from the cap 12 to provide a holding force for retaining the injection
pen 10 in the user's pocket, purse, or carrying case. One or more windows 15 may also
be provided in the cartridge holder 14 to give a visual indication of the medication
volume remaining in the cartridge 36.
[0017] An exploded perspective view of a pen needle 11 of an exemplary injection pen is
shown in FIG. 2C. The pen needle 11 includes the cover (outer shield) 1, an inner
shield 2, a needle cannula 5, and a hub 3. During manufacture, a proximal end of the
needle cannula 5 is inserted into a center opening in the distal (patient) end 4 of
the hub 3 until a predetermined length of the distal (patient) end of the needle cannula
5 remains extended. The needle cannula 5 is secured by epoxy or adhesive in the distal
end 4 of the hub 3. To protect users from injury and the needle cannula 5 from being
damaged, the inner shield 2 covers the exposed portion of the needle cannula 5. The
open proximal end of the inner shield 2 is placed over the exposed portion of the
needle cannula 5. The open proximal end of the cover 1 envelops the inner shield 2,
needle cannula 5, and hub 3. The distal end of the cover 1 is closed to prevent contamination
and damage to the inner components of the pen needle 11, and to prevent injury to
anyone who may handle it prior to use. When the user is ready to use the pen needle,
the hub 3 is screwed onto threads 42 of cartridge holder 14 of the injection pen 10
(FIGs. 1, 2A and 2B), and the cover 1 and shield 2 are separately removed from the
hub 3/cannula 5 subassembly by a pulling action. The distal end of the inner shield
2 is closed to protect the user from an accidental needle stick by the needle cannula
5 after the cover 1 is removed. The inner shield 2 is then removed to access the needle
cannula 5.
[0018] With reference to FIGs. 3A and 3B, the body 18 is generally cylindrical, and includes
a cylindrical partition or wall 50 extending across the interior of the body 18 through
which a channel 51 is formed comprising an aperture 52. Cylindrical wall 50 effectively
divides body 18 into two compartments, a first compartment proximal to wall 50 for
housing the plurality of dose setting and injecting components, as shown in FIGs.
2A and 2B, and a second compartment distal of wall 50 for housing the leadscrew brake
32 and connecting to the cartridge holder 14. The channel 51 comprises internal threads
54 threadedly engaging corresponding threads of the leadscrew 26. In an exemplary
embodiment, the leadscrew 26 is provided with a non-circular cross-section, in which
case, the aperture 52 is defined to allow rotational and thereby axial movement of
the leadscrew 26 therethrough. A plurality of second threads 56 are provided on the
interior of the body 18 in the first compartment and threadedly engaged with corresponding
threads 62 provided on the dose set knob 20, as discussed further below. Body 18 preferably
includes a window 57 enabling the user to view a set dose indicated on the outer surface
of the dose set knob 20. As described further below, a series of angled steps or teeth
55 are provided on the interior of the second compartment of body 18, circumferentially
surrounding the distal end of channel 51. Teeth 55 are provided as part of a unidirectional
coupling with the leadscrew brake 32 to allow the leadscrew 26 to rotate through the
channel 51 in only one direction, that which causes the leadscrew to expel medication
from cartridge 36. In an exemplary embodiment, body 18 also includes a circumferential
rib or groove 58 onto which the cartridge holder 14 may be mounted with a snap fit.
[0019] With reference to FIGs. 4A and 4B, a generally cylindrical dose set knob 20 with
open proximal and distal ends is provided with an enlarged proximal portion or handle
60 defining a knob-like feature. Handle 60 may include a plurality of grooves 61 enabling
a user to securely grip handle 60 to set a dose of medication for an injection. Dose
set knob 20 includes at least one thread element 62 provided on its external surface,
preferably near the distal end and threadedly engaging corresponding threads 56 on
the interior of body 18. An injection dose is set by the user by rotating dose set
knob 20 in a predetermined direction. Due to the threaded engagement with the body
18, rotation of the dose set knob 20 translates into axial movement of the dose set
knob in the proximal direction extending away from and out of the body 18. Provided
on the outer surface of body 18, are a plurality of dosing indicia (not shown) indicating
a set dose to be viewed through window 57 provided on body 18.
[0020] A plurality of radially directed ridges 63 are provided circumferentially along the
interior surface of dose set knob 20 adjacent to handle 60. Ridges 63 provide part
of a clicking means in conjunction with an externally directed ratchet element 82
provided on click arm 81 (FIG. 6A, 6B) of click element 30. Ridges 63 each comprise
a sloped edge and a flat face for allowing relative rotational movement between the
dose set knob 20 and click element 30 in only one direction in which the click arm
81 is enabled to slide over ridges 63, thus providing an audible and tactile signal.
Additionally, the proximal edges of ridges 63 define a proximally facing surface having
a plurality of teeth 64 disposed thereon. In an exemplary embodiment, teeth 64 are
included as part of a clutch mechanism when engaged with corresponding teeth 74 (FIGs.
5A and 5B) disposed on setback member 22. When pressed together during injection,
teeth 64 and 74 lock together, thus preventing relative rotation between setback member
22 and dose set knob 20, as further described below. Additionally, during dose setting,
teeth 64 provided on the dose set knob 20 function as a shelf, causing axial movement
of the setback member 74 together with the dose set knob 20, as the dose set knob
is rotated and moved axially out of the body 18. Dose set knob 20 also includes a
plurality of longitudinally extending keys or splines 65 provided substantially along
the interior surface preferably extending from the open distal end to the enlarged
proximal portion 60. Longitudinal splines 65 engage with corresponding grooves 95
provided on the exterior of dose stop member 28 to prevent relative rotation between
the dose set knob 20 and the dose stop member 28, but to allow relative axial movement
therebetween.
[0021] Setback member 22 comprises a generally cylindrical elongated member as shown in
FIGs. 5A and 5B. Provided near the proximal end of setback member 22 are a plurality
of ridges 73 spaced along the external surface thereof. When the exemplary injection
pen 10 is assembled, ridges 73 of setback member 22 face ridges 63 provided on the
internal surface of dose set knob 20. Ridges 73 include sloped edges and flat faces
for engaging an internally directed ratchet element 84 provided on flexible arm 83
of click element 30. As similarly described above, ridges 73 enable relative rotational
movement between the setback member 22 and click element 30 in only one direction
in which the internally directed ratchet element 84 is enabled to slide over ridges
73 providing an audible and tactile signal. The allowed direction of relative rotation
between the setback member 22 and click element 30 is in the direction opposite that
enabled by similar engagement between the dose set knob 20 and the click element 30,
so that the relative rotation between dose set knob 20 and setback member 22 is bi-directional.
[0022] Click element 30 is described with reference to FIGS. 6A and 6B. As shown, click
element 30 is a cylindrical tube like element comprising a plurality of radially flexible
arms 81 and 83 oppositely disposed from each other. The click element 30 is preferably
constructed with a longitudinal dimension similar to the length of the ridge portions
63, 73 provided on the dose set knob 20 and setback member 22, respectively. Flexible
arm 81 includes an externally directed ratchet element 82 provided at the free end
thereof facing ridges 63 provided on the interior of dose set knob 20. Flexible arm
83, on the other hand, includes an internally directed ratchet element 84 provided
at the free end thereof facing ridges 73 provided on the exterior of setback member
22. During dose setting, click element 30 is permitted to rotate relative to both
the setback member 22 and dose set knob 20, but in only one direction with respect
to each. In other words, during dose setting, click element 30 is rotationally locked
to one of the setback member 22 or the dose set knob 20 via flexible arms 83 and 81,
respectively, depending on the direction of relative rotation for either normal setting
of a dose or dialing back of the set dose. When the dose set knob 20 is rotated in
the direction in which ridges 63 are enabled to slide over the externally directed
ratchet element 82 and produce an audible signal, the click element 30 does not move
rotationally relative to the setback member 22 since such a movement is prevented
by an engagement between click arm 83 and ridges 73. Conversely, when the dose set
knob 20 is rotated in the opposite direction, the externally directed ratchet element
82 engages with one of the ridges 63 causing the click element to rotate together
with the dose set knob 20. In this case, the internally directed ratchet element 84
is now permitted to slide past ridges 73 on the setback member, thereby producing
an audible signal.
[0023] The exemplary construction of click element 30 described above allows relative rotation
in both directions between the setback member 22 and the dose set knob 20. Such a
click element is not restricted to the design depicted in FIGs. 6A and 6B. Any similar
element(s) enabling bi-rotational movement between setback member 22 and dose set
knob 20, as described above, may be implemented in this embodiment, as would be evident
to one of ordinary skill in the art.
[0024] As shown in FIG. 5A, setback member 22 includes an adapter element 71 for snap-fitting
with an internal cavity of push button 34. Push button 34 is of any conventional design,
but it is preferred that the snap engagement enables the push button to freely rotate
on the adapter element 71. Alternatively, push button 34 may be unitarily formed with
the adapter element 71. Additionally, as shown in FIG. 5B, a plurality of longitudinally
extending keys or splines 75 are provided along the internal cylindrical surface of
setback member 22. Splines 75 are formed to engage corresponding longitudinal grooves
85 provided on the external surface of driver member 24, shown in FIG. 7, thus preventing
relative rotation between the setback member 22 and driver 24, while allowing relative
axial movement therebetween. With reference to FIG. 7, the driver 24 includes open
proximal and distal ends which provide a passage 86 for leadscrew 26. In an exemplary
embodiment, passage 86 comprises a non-circular cross-section corresponding to the
non-circular cross-section of leadscrew 26, thus preventing relative rotation therebetween.
Driver 24 includes a disk 87 formed at the proximal end for snap-engaging with at
least one flexible tab 97 provided on the interior surface of dose stop element 28
(FIG. 8A). With the snap engagement, the driver 24 is fixed axially relative to the
dose stop element 28, yet is able to rotate relative thereto. Driver 24 may also include
one or more flexible legs 88 inwardly biased to engage leadscrew 26. Flexible leg
88 may be provided to reduce any play between the mating cross sections of leadscrew
26 and aperture 86 to improve dose accuracy of the exemplary injection pen 10.
[0025] With reference to FIGs. 8A and 8B, a generally cylindrical dose stop element 28 is
provided for enabling last dose control so that a dose cannot be set or dialed up
that is greater than the amount of medication remaining in the cartridge 36, as further
discussed below. Dose stop element 28 includes a plurality of longitudinal grooves
95 on the external surface thereof. Grooves 95 engage with corresponding splines 65
provided on the interior of dose set knob 20, thereby preventing relative rotation
therebetween, but allowing relative axial movement. Dose stop element 28 has an open
proximal end 91 and open distal end 92, the distal end 92 preferably comprising a
section of reduced diameter. Open distal end 92 defines a threaded opening with threads
93 disposed thereon for threadedly engaging corresponding threads 25 of the leadscrew
26 when assembled. Proximal end 91 defines a cavity housing setback member 22, driver
24, and leadscrew 26. Flexible tabs 97 are provided adjacent to the open distal end
92, extending into the interior of the dose stop element 28. A recess 96 or cutout
is provided in the external cylindrical wall of the dose stop element defining an
area into which flexible tabs 97 are allowed to flex. During assembly, driver 24 is
inserted into the open proximal end 91, upon which disk 87 disposed near the distal
end of driver 24 engages flexible tabs 97, and causes them to flex outwardly into
recess 96 until the disk 87 moves past the flexible tabs, at which time the flexible
tabs 97 return to their initial positions to provide a blocking surface for the driver
24, preventing relative axial movement therebetween.
[0026] While the above components are described as comprising specific features for engaging
and interconnecting other components of an exemplary injection pen, the above components
are not limited to these specific features. For instance, instead of the described
mating non-circular cross-sections to prevent relative rotation between leadscrew
26 and driver 24, one of ordinary skill in the art will appreciate that similar functionality
may be provided using a spline/groove engagement for preventing relative rotation
therebetween while also allowing relative axial movement. Conversely, the above described
spline/groove features may be replaced with non-circular mating arrangements or other
known features for preventing relative rotation while allowing relative axial movement
therebetween.
[0027] With reference to FIGs. 9A and 9B, leadscrew brake 32 comprises a generally cylindrical
housing portion 90 provided with a first diameter large enough to surround channel
51, as shown in FIG. 9B. Extending in the distal direction, a pair of wall portions
92 is provided defining an aperture 93 with a non-circular cross-section to mate with
the non-circular cross section of leadscrew 26. Due to the mating non-circular aperture
93, the leadscrew 26 is prevented from rotating with respect to the leadscrew brake.
Further, the leadscrew brake 32 comprises a pair of flexible ratchet arms 94 configured
to engage the cylindrical ring of ratchet teeth 55 provided on the interior of the
body 18 to define a unidirectional coupling therebetween. Ratchet arms 94 are configured
to allow rotation of the leadscrew brake 32, and therefore the leadscrew 26, in only
one direction with respect to the body 18. The allowed direction is that which causes
the leadscrew 26 to rotate through the threaded channel 51 in the distal direction
to expel medication. During injection, the leadscrew brake 32 rotates relative to
body 18, and ratchet arms 94 ride over the slanted or ramped portion of teeth 55 to
produce an audible clicking signal indicating the injection is being performed. Rotation
of the leadscrew brake in the opposite direction causes the free ends of ratchet arms
94 to engage the flat faces of teeth 55, which resist ratcheting of the ratchet arms
94 and thereby prevent relative rotation in this direction. Due to the unidirectional
coupling between leadscrew brake 32 and teeth 55, an undesired rearward movement of
the leadscrew 26 is prevented.
[0028] Having described exemplary structures, features and interrelationships between particular
elements of the exemplary embodiment of medication injection pen 10 herein, the intended
functionality of such an exemplary medical pen device will now be described.
[0029] Following assembly of the exemplary elements as shown in FIGs. 2A, 2B, and as described
above, to set a desired dose, the patient or user first grips and rotates the enlarged
proximal end 60 of the dose set knob 20. The dose set knob 20 is rotated a number
of rotations relative to the body 18 until a desired dose is shown through the window
57 on the body 18. Due to the threaded engagement of thread 62 on the dose set knob
20 with the internal thread 56 of the body, the dose set knob is caused to screw out
of the proximal end of the body, carrying the setback member 22 along with it by substantially
the same distance. The dose stop member 28 is also caused to rotate together with
the dose set knob 20 due to the spline/groove engagement between spline 65 provided
on the interior of the dose set knob 20 and groove 95 provided on the exterior of
dose stop 28. Rotation of the dose stop member 28 causes axial movement of the dose
stop member with respect to the body 18 in the proximal direction due to the threaded
engagement between threads 93 on the dose stop member and threads 25 of the leadscrew
26. The dose stop element 28, however, moves a shorter distance axially than the dose
set knob 20 due to a difference in the pitch of the thread 25 of the leadscrew 26
and the inner thread 56 of the body 18.
[0030] During normal dose setting for increasing a set dose, the leadscrew 26 is prevented
from rotating with respect to the body 18 in the dose setting direction due to the
unidirectional coupling between the leadscrew brake 32 and the teeth 55 disposed on
the body 18. Setback member 22 and driver 24, which are rotationally fixed to each
other due to spline/groove connection 75/85, are therefore also prevented from rotating
with respect to body 18 during dose setting, since the driver is rotationally fixed
to the leadscrew via the mating of the non-circular cross-section of leadscrew 26
and the non-circular aperture 86 of the driver 24. Due to the snap fit between disk
87 of the driver 24, and flexible tabs 97 provided on the dose stop member 28, as
the dose stop member screws out of the body in the proximal direction, the driver
24 moves axially by the same distance, but does not rotate.
[0031] The setback member 22 is interconnected to the dose set knob 20 through the bi-directional
click element 30. During normal dose setting, the dose set knob 20 rotates relative
to the click element 30, and thus an audible signal is provided due to the inner grooves
63 of the dose set knob 20 sliding past the externally directed ratchet element 82
on flexible arm 81. The externally directed ratchet element 82 tends to slide past
ridges 63 in the dose setting direction because the internally directed ratchet element
84 of flexible arm 83 is locked with the ridges 73 provided on the setback member
22, which is prevented from rotating in this direction due to its engagement with
the driver 24 and leadscrew 26.
[0032] If the user initially sets a dose larger than desired, the set dose can be "dialed
back" or reduced by simply turning the dose set knob 20 in the opposite direction.
Rotation of the dose set knob 20 in this reverse direction, which is the direction
of injection, would normally cause rotation of the leadscrew 26 and thus axial movement
of the leadscrew into the cartridge 36. During injection, rotation of the leadscrew
26 is effected due to the coupling between teeth 64 on the dose set knob and teeth
74 on the setback member 22, which is indirectly rotationally fixed to the leadscrew
26. During dial back, however, the dose set knob 20 and setback member 22 are not
coupled via teeth 64/74 and the dose set knob 20 rotates in this reverse direction
relative to the setback member 22 through the click element 30. Reverse rotation of
the dose set knob 20, during dial back, now causes the internal ridges 63 on the dose
set knob 20 to engage and lock with the externally directed ratchet element 82, forcing
the click element 30 to rotate in this same direction. The internally directed ratchet
element 84 is now caused to slide over ridges 63 provided on the setback member 22,
thereby producing an audible signal indicating the dose is being reduced. Ratchet
element 84 tends to slide over ridges 73 in this direction since there is less friction
provided between ratchet element 84 and ridges 73 than there is between the unidirectional
coupling between the leadscrew brake 32 and the body 18. In other words, the force
required to dial back a set dose is not great enough to overcome the friction between
the ratchet arms 94 of leadscrew brake 32 and the teeth 55 of body 18.
[0033] Once a desired dose is set, and the user desires to inject the set dose of medication,
the medical injection pen 10 is applied to the skin of the patient to insert the needle
cannula 5. The pen needle 11 is attached to the threaded portion 42 of the cartridge
holder 14 prior to or after setting the desired dosage, as a matter of user preference.
Once the pen needle 11 has been attached to the cartridge holder 14 and inserted into
the patient, the push button 34 is depressed. The axial force applied to the push
button 34 by the user causes the teeth 74 on the setback member 22 to engage with
the teeth 64 on the dose set knob 20 to mesh and rotationally lock the setback member
22 with the dose set knob 20, forming an injection coupling. The applied force causes
the dose set knob 20 (due to a non self-locking threaded engagement with the body
18 via threads 56 and 62) to rotate in the direction opposite that which occurs during
normal dose setting. This rotation is now imparted to the setback member 22 and therefore
the driver 24 (due to the spline/groove connection 75, 85). Since the driver 24 mates
with the non-circular cross-section of the leadscrew 26, the leadscrew is also caused
to rotate relative to body 19, which translates into axial movement of the leadscrew
into the cartridge 36 to expel a dose (due to the threaded engagement between threads
25 on the leadscrew and threads 54 disposed on channel 51 of the body 18). Axial movement
of the leadscrew in the distal direction urges the spinner 16 against the plunger
40 to expel medication from the cartridge 32. The injection force is greater than
the frictional force in the leadscrew brake 32, and hence the leadscrew brake allows
rotation of the leadscrew 26 in this direction during injection. As the leadscrew
brake 32 rotates with the leadscrew 26, oppositely disposed ratchet arms 94 slide
over the teeth 55 disposed on the interior of body 18 to produce a clicking sound
as the injection is carried out.
[0034] The dose administration process described above may be repeated until the medication
in the cartridge 36 is spent. Prior to expelling the last dose from the cartridge
36, it is desired to ensure that the last dose expelled is consistent with the dose
set by the user. In other words, the user should not be able to set a dose for an
amount greater than the remaining volume of medication in the cartridge 36. This last
dose control is realized when threads 93 disposed on the dose stop element 28 abut
against a non-threaded portion of the leadscrew 26 at its proximal end, preventing
further rotation of the dose stop member 28 on leadscrew 26. When this occurs, the
indicia on the dose set knob 20, read through window 57, indicate the last remaining
injectable volume of medication in the cartridge 36. Once the dose stop member 28
is prevented from rotating further, the dose set knob 20 is also prevented from further
rotating in this direction for setting a larger dose, due to the spline/groove engagement
65/95 between dose set knob 20 and dose stop member 28.
[0035] During dose setting, the dose stop member 28 changes its relative position on the
leadscrew 26 based on the number of rotations of the dose set knob 20. Axial movement
of the dose stop member 28 during dose setting is by substantially the same distance
as the leadscrew 26 moves into cartridge 36 during injection. The length of axial
movement of leadscrew 26, and therefore the volume of medication to be expelled, is
determined in part by the thread pitch of the leadscrew threads 25 and threads 54
of the body, which is substantially the same as the pitch of the threads 93 of the
dose stop member 28. Thus, the relative position of the dose stop member 28 on the
leadscrew 26 throughout administration is indicative of the remaining dosage amount
in the cartridge 36. The dose stop member maintains its relative position on the leadscrew
26 during injection due to its spline/groove engagement 65/95 with the dose set knob
20. During injection, the dose sent knob 20, dose stop member 28, setback member 22,
driver 24 and leadscrew 26, are all rotationally locked together. Since the threads
93 of the dose stop member 28 and the threads 54 of the body 18 are of substantially
the same pitch, simultaneous rotation of the dose stop member 28 and leadscrew 26
results in the same axial movement. Thus, during injection, the dose stop member 28
does not move axially relative to leadscrew 26, and therefore maintains its relative
position with respect to the leadscrew as determined during the dose setting procedure.
After administration of the last dose, if the injection pen 10 is reusable, the cartridge
can be replaced, whereas, if the pen is disposable, the entire pen 10 may be disposed
of.
[0036] As will be appreciated by those skilled in the art, various modifications can be
made to the above exemplary embodiments without substantially altering the functionality
of the injection pen 10. For example, such modifications may be made to ease the assembly
of the various components, reduce the complexity of manufacturing, reduce the number
of elements, or provide some additional improved functionality. Some such exemplary
modifications are described below.
[0037] In one alternative embodiment, teeth 64 on the dose set knob 20, described above
as part of an injection coupling with corresponding teeth 74 (FIGs. 5A and 5B) disposed
on setback member 22, can generate dose setting click signals in the absence of click
element 30. A spring element or wave washer with similar functionality may be provided
to bias the teeth 74 of setback member 22 toward the corresponding teeth 64 provided
on the dose set knob 20, so that they are in constant meshed engagement. The spring
force, however, is easily overcome by relative rotation between the dose set knob
20 and setback member 22, which causes the corresponding teeth 64/74 to slip over
each other producing an audible and tactile signal.
[0038] In another exemplary embodiment, an alternate injection coupling is provided between
a modified dose set knob 20 (teeth 64 removed) and a modified setback member 22',
shown in FIG. 10. In this embodiment, the injection coupling described above with
respect to teeth 64 on the dose set knob 20 and corresponding teeth 74 on the setback
member 22, is replaced by an extended surface 101 provided near the proximal end of
the setback member 22', the extended surface 101 being defined by a larger diameter
with respect to ridges 73. Click element 30 includes a first surface 102 positioned
co-axially on and surrounding the extended surface 101. During the dose setting operation,
click element 30 is positioned on setback member 22', such that click arms 81 and
83 are free to flex and slide past ridges 73 and 63, respectively. In this embodiment,
the dose setting and dial back mechanism is unchanged. During injection, however,
upon the user applying an injection force to push button 34, the setback member 22'
is pushed into the dose set knob 20 and into click element 30. As the setback member
22' moves axially toward click element 30, the extended surface 101 is moved into
engagement with click arm 83, as shown in FIG. 10B. In this position, click arm 83
is prevented from flexing radially inward to slide past grooves 63 in the dose set
knob, thus locking click element 30 to dose set knob 20. Relative rotation of the
dose set knob 20 with respect to the setback member 22' in this direction during dose
setting would have enabled the ratchet arm 83 to ride over ridges 63 to reduce a set
dose. During injection, however, ratchet arm 83 is now prevented from flexing away
from ridges 63, and thus prevented from sliding over ridges 63, by the blocking engagement
of extended surface 101. Accordingly, the setback member 22' is now rotationally locked
to dose set knob 20 via nonsliding engagement with ratchet arm 83, thus enabling injection
of a set dose, as described above.
[0039] In another embodiment, the exemplary injection pen 10 is modified to facilitate the
manufacture of injection pens providing different dosing needs. For example, an injection
pen for administering a first medication may desire finer dosing intervals for more
precise dosage control than that of another medication. To utilize the same dose setting
and injection functionality of the exemplary injection pen described above, it is
desired to be able to provide a plurality of pens meeting the various dosing needs
with greater compatibility, so as to reduce the complexity of manufacturing multiple
such pens.
[0040] One such modification is made to the embodiment illustrated in FIG. 9B to switch
the ratchet arms 94 provided on the leadscrew brake 32 with the ratchet teeth 55 provided
on body 18, as shown in FIG. 11A. As shown, the body 18' now includes ratchet arms
111 and the leadscrew brake 32' now includes teeth 112. Engagement between ratchet
arms 111 and teeth 112 serves to provide similar unidirectional functionality as described
in the previous embodiment. Leadscrew brake 32' in this alternative embodiment facilitates
a change in a desired injection click interval necessitated by a desired change in
a dosing interval. For example, the injection clicks realized by relative rotation
of the leadscrew brake 32' preferably correspond to a dose increment, and are related
to the spacing of the teeth 112. If the dose increment is changed to have a greater
or smaller interval, a leadscrew brake with a corresponding spacing of teeth 112 is
assembled in the injection pen as shown, as opposed to providing a new body 18 with
the desired spacing of teeth 55, as in the earlier embodiment. The smaller leadscrew
brake 32 is easier and less costly to manufacture than the body 18, and hence it is
advantageous to replace leadscrew brake 32 in the modified injection pen as opposed
to replacing the body 18.
[0041] A further modification, shown in FIGs. 11B-11F, enables an easier change of the thread
pitch of the leadscrew if desired to increase or decrease a dose rate. For example,
the threads 25 of the leadscrew 26 may be modified to include a larger pitch, so that
the same number of rotations of the leadscrew results in greater axial movement of
the leadscrew into cartridge 36 and therefore a larger dose volume. In the previous
embodiment, if the threads 25 of the leadscrew 26 are modified, the threads 54 of
the body are also modified accordingly. The additional modification shown in FIG.
11B provides an insert 114 which replaces the features of the partitioning wall 50
and channel 51 with threads 54 disposed thereon of the exemplary embodiment (see FIG.
3A). Insert 114 is a nut-like element with ratchet arms 115 disposed thereon. Insert
114 comprises a wall 118 with an aperture 119 therethrough. Aperture 119 is defined
by a cylindrical channel 116 with threads 117 disposed on the interior thereof. Body
18" now includes a shelf or ledge 121 forming a contact surface engaging with a proximal
surface of insert 114 to determine axial placement of the insert 114 into body 18".
Shelf 121 comprises at least one protrusion member 122 configured to engaged a corresponding
recess 120 on the proximal face of insert 114. Engagement between protrusion 122 and
recess 120 prohibits relative rotational movement between insert 114 and body 18".
Alternatively, any similar key/groove type structure may be provided to limit relative
rotational movement between insert 114 and body 18".
[0042] Insert 114 may also be provided with an additional molded spring feature 124 to maintain
the positioning of insert 114 against shelf 121 in body 18". Molded spring feature
124 also presses against cartridge 36, as shown in FIG. 11F, to prevent the cartridge
from moving when the needle 5 is inserted into the cartridge septum 38 prior to injection.
This feature provides greater accuracy in dose injection and prevents undesired wasting
of medication. In prior art injection pens, the cartridge may be allowed to move a
slight distance in the proximal direction during this operation, resulting a small
waste or "drool" of the medication.
[0043] In another exemplary embodiment, an end of injection click or signal is provided
by a modified dose set knob 20' including a radially flexible leg 128 near the distal
end of dose set knob 20' extending in the distal direction. Flexible leg 128 interacts
with an angled protrusion 130, shown in FIG. 12B, disposed on a proximal surface of
partitioning wall 50 of the body 18. Angled protrusion 130 is preferably fixed to
partitioning wall 50 at only one end, which is the end spaced farther away from the
internal surface of body 18. At a zero dose position, when the dose set knob 20' abuts
partitioning wall 50, flexible leg 128 is positioned near protrusion 130, but not
in touching engagement. Upon setting of a desired dose, as the dose set knob 20' is
rotated, flexible leg 128 moves between the angled protrusion 130 and an internal
surface of body 18, as shown in FIG. 12C. Since the angled protrusion 130 is not fixed
to the partitioning wall 50 at the end closest to the internal surface of the body
18, the angled protrusion flexes radially to allow passage of the flexible leg therebetween
and reduce the friction for initially overcoming the protrusion during dose setting.
Once flexible leg 128 passes behind protrusion 130, continued rotation of the dose
set knob 20' will result in axial movement of the dose set knob away from partitioning
wall 50 so that the flexible leg 128 no longer interacts with protrusion 130. Normal
setting of the dose is now performed.
[0044] As the set dose is injected, dose set knob 20' screws back into body 18 and moves
toward partitioning wall 50. As the injection is nearing its end, flexible leg 128
once again engages protrusion 130 as shown in FIG. 12E. This time, as flexible leg
128 abuts against protrusion 130, it is not allowed to pass between the protrusion
130 and the internal surface of body 18. Now, the flexible leg 128 is caused to flex
radially inward to slide past protrusion 130 until it moves past the end of protrusion
130, at which time flexible leg 128 snaps against the internal surface of body 18
providing an audible and tactile signal. At this point, the set dose is completely
delivered and the injection pen is at a zero dose position.
[0045] In one embodiment, an end of dose click may be provided as a distinct signal distinguishable
from the injection clicks provided by the leadscrew brake 32 as discussed above with
respect to FIG. 9. In another embodiment, however, the injection clicks are muted,
and a user senses only the end of injection click provided between the flexible leg
128 and protrusion 130. One way to mute the injection clicks is to replace ratchet
teeth 55 provided on the body 18 with a rubber like ring or brake 134, as shown in
FIG. 13. During injection, the leadscrew brake 32 still rotates with respect to body
18, but in this embodiment, ratchet arms 94 slide along the surface of the rubber
brake 134 without providing an audible or tactile signal. Rubber brake 134 is fixed
to the body 18 using an adhesive or other structure, so that it does not rotate relative
to the body 18, and therefore is still capable of functioning as a unidirectional
coupling with leadscrew brake 32. Ratchet arms 94 of the leadscrew brake 32 are preferably
beveled or otherwise configured to grip the rubber brake 134 to prevent relative rotation
therebetween, similar to the embodiment discussed in FIG. 9B. Additionally, one of
ordinary skill in the art will appreciate that rubber brake 134 may be modified as
similarly discussed in FIG. 11A and 11B.
[0046] In another exemplary embodiment, an element or elements are added to improve the
mechanical efficiency of an exemplary injection pen 10, by eliminating or reducing
the friction between elements rotating relative to each other or those moving axially
with respect to each other. One particular engagement with undesirable friction is
between the push button 34 and the adapter element 71 provided on the setback member.
During dose setting and injection, push button 34 preferably rotates freely on adapter
element 71. In an exemplary embodiment, as partly shown in FIG. 5A, adapter element
71 includes a point 77 provided at the center of the axis of rotation of the setback
element 22. This point 77 contacts push button 34 near its center of rotation. Providing
such a contact surface between these elements at or near the center of rotation reduces
frictional torque between these elements during relative rotation, and thereby increases
efficiency. To further reduce the friction between setback member 22 and push button
34, one embodiment includes at least one rolling ball (i.e. ball bearing) 140 situated
between an internal surface of the push button 34 and a surface of the adapter element
71, as shown in FIG. 14A. Rolling balls 140 function to translate sliding friction
between engaging elements into a reduced rolling friction. In another embodiment,
shown in FIG. 14B, a pair of magnets 142a and 142b with the same polarity are provided
on adjacent contact surfaces facing each other. For instance, a first magnet 142a
is provided on the interior of push button 34, whereas the second magnet 142b is provided
on a contact surface of adapter element 71 facing the first magnet. Due to the same
polarity between magnets 142a and 142b, the resulting repulsion force reduces the
contact force between these two surfaces, thus reducing friction therebetween without
affecting the push force required for injecting medication. One of ordinary skill
in the art will appreciate that the above methods may also be implemented in combination.
Further, such methods may be implemented between any two components with a linear
or rotational contact surface, to further improve mechanical efficiency.
[0047] The exemplary embodiments described above may be provided as a reusable or disposable
pen. In a disposable implementation, cartridge holder 14 and body 18 are preferably
irreversibly assembled. In one embodiment, as described with respect to FIG. 3A, a
circumferential rib provided on the cartridge holder 14 snaps into engagement with
a groove 58 on body 18. In another embodiment, shown in FIG. 15A, threaded insert
114 may include at least one tab 125 for snap-fitting with a recess 126 provided on
cartridge holder 114. Since threaded insert 114, as discussed with respect to FIGs.
11B and 11C, is fixed both axially and rotationally to body 18, snap-engagement of
the cartridge holder 14 to threaded insert 114 prevents relative rotation between
the cartridge holder and the body.
[0048] In a preferred embodiment shown in FIG. 15B, cartridge holder 14 and body 18 comprise
a set of threads 151 and 152 which provide a secure threaded coupling between the
cartridge holder 14 and body 18. Additionally, one of the cartridge holder and the
body comprises a snap 154 and the other comprise a recess 156 for engaging snap 154.
The snap/recess engagement is preferably a one-way radial snap. Thus, once the body
18 and the cartridge holder 14 are screwed together, the snap 154 moves into engagement
with recess 156 until they snap together providing a secure, irreversible connection,
with minimal or no play between the cartridge holder 14 and body 18, thereby increasing
accuracy of the dose injection and reducing/eliminating unnecessary waste of medication.
[0049] In view of the above description, another exemplary embodiment comprising similar
components and functionality is shown in FIGs. 16A and 16B. The components shown in
FIGs. 16A and 16B have similar functionality to those described above, unless noted
otherwise, and therefore their detailed description is omitted herein. In this embodiment,
body 218 is similar to the body 18" shown in FIGs. 11B and 11D. A first compartment
defined by the interior of body 218, proximal to wall 250, houses a dose set knob
220, a setback member 222, a dose stop member 228, a driver 224, and a leadscrew 226.
The second compartment defined by the interior of body 218, distal to wall 250, houses
a threaded drive insert 233 and a distal end 225 of driver 224. Wall 250 is provided
with an aperture sized to fit the main cylindrical body of driver 224, but not the
enlarged distal end 225, as shown in FIG. 16B, thus axially fixing the driver 224
to the body 218.
[0050] In this embodiment, the leadscrew 226 has a circular cross-section, and is rotatably
fixed to driver 224 via a key/groove engagement as shown in FIG. 17. A proximal end
of leadscrew 226 includes keys 217 engaging in longitudinal grooves 223 provided on
the interior of driver 224. Via this key/groove engagement, the leadscrew 226 is rotationally
fixed to the driver 224 but is allowed to move axially relative thereto. Driver 224
comprises longitudinal grooves 285 engaging internal keys or splines 275 provided
on the interior of setback member 222 to rotationally lock the driver 224 thereto.
Driver 224 now includes an enlarged distal end 225 provided with a ring of teeth 255
circumferentially disposed thereon and functioning similarly to the toothed leadscrew
brake 32' in FIGs. 11A and 11B. Distal end 225 comprises part of a unidirectional
coupling along with the threaded insert 233, as similarly discussed above with respect
to FIGs. 9B and 11B. Threaded insert 233 comprises an aperture with threads disposed
thereon, which are threadedly coupled to corresponding threads on leadscrew 226, similar
to insert 114 of FIG. 11C.
[0051] In this embodiment, last dose control is provided by a modified dose stop member
228, as shown in FIG. 18. Dose stop member 228 comprises a ring link structure provided
with a series of threads 290 disposed on the exterior surface thereof and threadedly
engaged to threads 291 disposed on the dose set knob 220. Dose stop member 228 is
rotationally fixed to setback member 222 via corresponding ridges 272 provided on
the interior surface of dose stop member 228, which mesh with similar ridges 273 disposed
on the setback member, as shown. In this embodiment, as the dose set knob 220 is rotated
to set a desired dose or decrease a too-large dose, dose stop member 228 screws into
threads 291 disposed on the dose set knob by an amount related to the set dose. During
injection, the dose stop member 228 maintains its relative position with respect to
threads 291, since the setback member 228 is rotationally fixed to the dose set knob
220. Therefore, dose stop member 228 and dose set knob 220 rotate together and there
is no relative movement therebetween. Once the dose stop member 228 screws into the
end thread of the threads 291, it is prevented from rotating further, and thus further
rotation of the dose set knob to set a larger dose is also prevented. Such an occurrence
indicates a final dose of medication remaining in the cartridge.
[0052] To set a desired dose for injection the user rotates the dose set knob 220. Audible
clicking of the set dose is provided by slipping of teeth 264 on dose set knob 220
with teeth 274 on setback member 222, as similarly described in the previous embodiment
above. Teeth 264 and 274 are held in meshed engagement by a spring element 233 provided
within push button 234. Similar to the previous embodiment, when the user presses
push button 234 to inject a dose, the setback member 222 is rotationally locked to
the dose set knob 220 via engagement between the teeth 264 and 274. Setback member
222 now rotates with dose set knob 220, as the dose set knob screws back into body
218. Rotation of the setback member 222 translates to driver 224 which rotates the
leadscrew 226. The leadscrew 224 rotates through the fixed threaded drive insert 233
and into the cartridge to expel a dose. As the driver 225 rotates in this direction,
the distal ring of teeth 255 provides the injection clicking as teeth 255 slip past
ratchet arms disposed on threaded drive insert 233.
[0053] In another embodiment, last dose control is similarly provided with a modified dose
stop element 328, as shown in FIG. 19A. Dose stop element 328 is a half-nut like member
with a series of threads disposed on the internal surface thereof, threadedly engaging
threads 332 provided on threaded setback member 322. Dose set knob 320 comprises two
longitudinally extending ribs or splines 330, circumferentially spaced from each other
by a distance substantially the same as the length of the dose stop element 328. Splines
330 engage corresponding edges of dose stop element 328 to rotationally lock the dose
stop element to the dose set knob 320. During setting of a dose, dose stop member
328 screws onto threads 332 of setback member 322, its relative position indicated
the remaining volume of medication in the cartridge. When the dose stop member 328
reaches an end of thread 332 or a fixed stop on either the dose set knob 320 or setback
member 322, dose stop element 328 is prevented from rotating further and thus limiting
the dose to that remaining in the cartridge.
[0054] Yet another embodiment, using a similar principle of operation, is shown in FIG.
19B. In this embodiment, dose stop element 428 is threaded along its outer surface
with threads 427. The inner surface of dose set knob 420 is provided with at least
one thread disposed thereon with a length sufficient to maintain constant engagement
with threads 427 of dose stop member 428. Setback member 422 comprises two longitudinally
extending ribs or splines 430, circumferentially spaced from each other by a distance
substantially the same as the length of the dose stop element 428. Splines 430 engage
corresponding edges of dose stop element 428 to rotationally lock the dose stop element
to the setback member 422. The outer surface of the setback member 422 in this embodiment
is provided with a substantially smooth surface to enable axial movement of dose stop
element 428 thereon. In this embodiment, the last dose volume is that indicated when
dose stop element 428 is prevented from moving any farther axially with respect to
setback member 422. Axial movement of dose stop element 428 is prevented when a first
edge of element 428 abuts a fixed stop in the dose set knob 420 or on the setback
member 422.
[0055] In view of the above description, yet another exemplary embodiment of an injection
pen comprising similar functionality is shown in FIG. 20. As shown in the cross-sectional
view, an exemplary injection pen in this embodiment comprises a main body 518, a dose
set knob 520, a setback member 522, a driver 524, a leadscrew 526, a dose stop member
528, and an insert 530. The body 518 is modified as shown in FIG. 21. As shown, at
least one ratchet arm 555, attached at one end of a sidewall of the body 18 distal
to the partitioning wall 550, is internally directed and preferably provided with
series of ridges or teeth 557 at the free end thereof. Teeth 557 engage with teeth
595 disposed on the outer surface of insert 530, as shown in FIG. 22. Teeth 557 are
forced into engagement with teeth 595 on the insert 530 when a cartridge holder is
attached to body 18, due to the cartridge holder engaging protrusion 559 provided
on the outer surface of ratchet arm 555. When the cartridge holder is attached to
the body 518, the insert 530 is prevented from rotating in either direction due to
the forced toothed engagement. When the cartridge holder is removed, such as to re-use
the injection pen, the ratchet arms 555 are free to ratchet and enable relative rotation
between the insert 530 and the body 518, to reload the leadscrew for subsequent use
of the injection pen. The insert 530 comprises an aperture 531 with a non-circular
cross-section for mating a similar non-circular cross-section of the leadscrew, to
prevent relative rotation therebetween. A plurality of teeth 556 are provided circumferentially
along an internal surface of the body 518 proximal to the partitioning wall 550. Teeth
556 serve to engage a ratchet element 586 provided near a distal end of driver 524,
as shown in FIG. 23, described further below.
[0056] As shown in FIG. 23, driver 524 comprises an elongated cylindrical member with open
distal and proximal ends for allowing passage of the leadscrew 526 therethrough. Driver
524 includes a plurality of splines 583 provided near the proximal end for engaging
corresponding grooves on the interior of setback member 522 for rotationally coupling
the driver 524 and setback member 522 together. A pair of protrusions 585 is provided
near the distal end of driver 524 for snap-engaging with the body 518 behind partitioning
wall 550. This snap-engagement prohibits relative axial movement between the driver
524 and the body 518 while allowing relative rotational movement therebetween. Driver
524 includes at least one thread element 582 provided on the interior surface for
threadedly engaging with a corresponding thread of the leadscrew 526. As discussed
further below, it is this thread engagement that forces the leadscrew 526 to move
axially in the distal direction to inject a set dose.
[0057] As shown in FIG. 24, the dose set knob 520 is an elongated cylindrical member provided
with an outer thread 562 threadedly engaging an internal thread of the dose set knob,
similar to the above embodiments. In this embodiment, the dose set knob 520 comprises
at least one ratchet arm 564 provided near the distal end thereof, for engaging a
plurality of ridges 573 provided on the outer surface of the setback member 522, as
shown in FIG. 25. The ratchet arm 564 includes a rounded protrusion 565 for enabling
slipping of the ratchet element in both directions over ridges 573 provided on setback
member 522, to provide audible click signals during both normal dose setting and dial-back.
Dose set knob 520 also includes a plurality of teeth 563 provided circumferentially
along an internal surface of the dose set knob, as shown. During dose setting, teeth
563 are situated in the recess 576 on the outer surface of the setback member, as
shown in FIG. 25. The teeth 563, in this embodiment, serve as an injection coupling
to rotationally lock the dose set knob 520 to the setback member 522. In another embodiment,
the injection coupling may be between a set of engaging teeth provided on the setback
member 522 and the dose set knob 520, as similarly discussed with respect to the first
embodiment shown in FIGs. 4A and 5A (teeth 64 and 74). Dose set knob 520 comprises
a plurality of threads 591 provided along the internal surface thereof for threadedly
engaging with threads 590 of the dose stop member 528.
[0058] Having described exemplary structures, features and interrelationships between the
particular elements of FIGs. 20-25, the intended functionality of such an exemplary
injection pen will now be described. Discussion of particular elements and features
similar to the above embodiments, have been omitted herein.
[0059] To set a desired dose for injection, a user rotates the dose set knob 520 in a first
direction. Relative rotation between the dose set knob 520 and the setback member
522 produces a series of dose-setting clicks due to the engagement between ridges
573 and ratchet elements 564, 565. If a too-large dose is set by the user, the user
can rotate the dose set knob 520 in a second, opposite direction to dial back the
set dose. During dose setting, the dose set knob is free to rotate in both the first
and second direction with respect to the setback member 522. To inject a set dose,
the user presses a push button 34, which pushes the setback member 522 in the distal
direction and causes ridges 573 on the setback member to engage teeth 563 provided
on the dose set knob. The dose set knob 520 and the setback member 522 are now rotationally
fixed with respect to each other. Now, as the dose set knob rotates back into the
body 518, the setback member 522 is also caused to rotate which forces driver 524
to rotate therewith. The leadscrew is prevented from rotating with respect to body
518 due to its mating engagement with the insert 530, which is rotationally fixed
to the body 518 when the cartridge holder is attached to the body 518, as described
above. Since the leadscrew 526 is rotationally fixed, relative rotation between the
driver 524 and the leadscrew 526 causes the leadscrew 526 to move axially into the
cartridge to inject a set dose, due to its threaded engagement with threads 582 provided
on the driver 524. During injection, as the driver 524 rotates relative to body 518,
ratchet arms 586 provide an injection click signal as they ride over teeth 556 provided
on the interior of body 518. In this embodiment, last dose control is performed similarly
to that described above with respect to FIG. 18, to prevent a user from setting a
dose larger than a remaining volume of medication remaining in the cartridge.
[0060] While the present invention has been shown and described with reference to particular
illustrative embodiments, it is not to be restricted by the exemplary embodiments
but only by the appended claims and their equivalents. It is to be appreciated that
those skilled in the art can change or modify the exemplary embodiments without departing
from the scope and spirit of the present invention.
FURTHER ASPECTS OF THE INVENTON ARE
[0061]
- 1. A medication injection pen comprising:
a housing;
a dose set knob comprising at least one internal thread and being rotatable with respect
to said housing to set a desired injection dose;
a leadscrew provided with a thread element and advanceable in a first direction via
a corresponding thread engagement, said first direction being that which expels medication
from a cartridge;
a driver rotationally fixed to said leadscrew for preventing relative rotation therebetween,
said driver being rotatable in a first direction to rotate said leadscrew and advance
said leadscrew in said first direction;
a setback member rotationally fixed to said driver for preventing relative rotation
therebetween; and
a dose stop member rotationally fixed to said setback member and comprising an external
thread in threaded engagement with said internal thread of said dose set knob, said
dose stop member being axially movable relative to said dose set knob when said dose
set knob is rotated relative to said setback member, and wherein axial movement of
said dose stop member limits a user from setting a dose that is greater than an injectable
volume of medication remaining in the cartridge.
- 2. A medication injection pen according to 1, wherein said dose stop member is rotationally
coupled to the setback member between a pair of longitudinally extending ribs provided
on said setback member.
- 3. A medication injection pen according to 2, wherein said dose stop member comprises
a partial nut situated on said setback member between said longitudinally extending
ribs.
- 4. A medication injection pen according to 1, wherein said dose stop member is rotationally
coupled to the setback member via engagement between corresponding ridges provided
on an internal surface of said dose stop member and an external surface of said setback
member.
- 5. A medication injection pen according to 3 or 4, wherein the axial movement of said
dose stop member is limited when a first edge of the dose stop member abuts a fixed
stop on said dose set knob or on said setback member.
- 6. A medication injection pen comprising:
a housing;
a dose set knob rotatable with respect to said housing to set a desired injection
dose;
a leadscrew provided with a thread element and advanceable in a first direction via
a corresponding thread engagement, said first direction being that which expels medication
from a cartridge;
a driver rotationally fixed to said leadscrew for preventing relative rotation therebetween,
said driver being rotatable in a first direction to rotate said leadscrew and advance
said leadscrew in said first direction;
a setback member provided with an external thread element and rotationally fixed to
said driver for preventing relative rotation therebetween; and
a dose stop member rotationally fixed to said dose set knob and comprising an internal
thread in threaded engagement with said external thread of said setback member, said
dose stop member being axially movable relative to said dose set knob when said dose
set knob is rotated relative to said setback member, and wherein axial movement of
said dose stop member limits a user from setting a dose that is greater than an injectable
volume of medication remaining in the cartridge.
- 7. A medication injection pen according to 6, wherein said dose stop member comprises
a partial nut, and is rotationally fixed to said dose set knob between a pair of longitudinally
extending ribs provided on said dose set knob.
- 8. A medication injection pen according to 7, wherein the axial movement of said dose
stop member is limited when a first edge of the dose stop member abuts a fixed stop
on said dose set knob or on said setback member.
- 9. A medication injection pen comprising:
a housing;
a dose set knob rotatable with respect to said housing to set a desired injection
dose;
a leadscrew provided with a thread element and advanceable in a first direction via
a corresponding thread engagement, said first direction being that which expels medication
from a cartridge;
a driver rotationally fixed to said leadscrew for preventing relative rotation therebetween,
said driver being rotatable in a first direction to rotate said leadscrew and advance
said leadscrew in said first direction;
a setback member rotationally fixed to said driver for preventing relative rotation
therebetween; and
a dose stop member rotationally fixed to said dose set knob and comprising an internal
thread in threaded engagement with said thread of said leadscrew, said dose stop member
being axially movable relative to said dose set knob when said dose set knob is rotated
relative to said setback member, and wherein axial movement of said dose stop member
limits a user from setting a dose that is greater than an injectable volume of medication
remaining in the cartridge.
- 10. A medication injection pen according to 9, wherein said dose stop member rotates
together with said leadscrew when said leadscrew rotates in said first direction.
- 11. A medication injection pen comprising:
a housing;
a dose set knob rotatable with respect to said housing to set a desired injection
dose;
a leadscrew provided with a thread element and advanceable in a first direction via
a corresponding thread engagement, said first direction being that which expels medication
from a cartridge;
a driver rotationally fixed to said leadscrew for preventing relative rotation therebetween,
said driver being rotatable in a first direction to rotate said leadscrew and advance
said leadscrew in said first direction;
a setback member rotationally fixed to said driver for preventing relative rotation
therebetween; and
a click element positioned between said dose set knob and said setback member, said
click element comprising a first arm member engaging an internal surface of said dose
set knob, and a second arm member engaging an external surface of said setback member,
wherein one of the said first and second arms produces an audible signal when said
dose set knob is rotated with respect to said housing.
- 12. A medication injection pen according to 11, wherein said internal surface of said
dose set knob and said external surface of said setback member each comprise a plurality
of teeth.
- 13. A medication injection pen according to 12, wherein said teeth of said dose set
knob are configured to allow relative rotation between said dose set knob and said
click element in a first direction, and said teeth of said setback member are configured
to allow relative rotation between said setback member and said click element in a
second opposite direction.
- 14. A medication injection pen according to 13, wherein when said dose set knob rotates
relative to said click element in said first direction, said first arm produces the
audible signal, and when said setback member rotates relative to said click element
in said second direction, said second arm produces the audible signal.
- 15. A medication injection pen comprising:
a housing;
a dose set knob rotatable with respect to said housing to set a desired injection
dose;
a leadscrew provided with a thread element and advanceable in a first direction via
a corresponding thread engagement, said first direction being that which expels medication
from a cartridge;
a driver rotationally fixed to said leadscrew for preventing relative rotation therebetween,
said driver being rotatable in a first direction to rotate said leadscrew and advance
said leadscrew in said first direction; and
a setback member rotationally fixed to said driver for preventing relative rotation
therebetween;
wherein said housing further comprises a flexible protrusion provided on a surface
within said housing, and said dose set knob further comprises a flexible tab element
which engages said protrusion to produce an audible signal upon completion of injection
of a set dose.
- 16. A medication injection pen according to 15, wherein when said dose set knob rotates
relative to said housing to set a desired injection dose, said flexible tab element
passes between a first edge of said protrusion and a sidewall of the housing, causing
said protrusion to flex away from said sidewall.
- 17. A medication injection pen according to 16, wherein said dose set knob rotates
in an opposite direction to inject a dose, and in this direction, said flexible tab
engages a second edge of said protrusion causing said flexible tab to flex radially
inward, wherein once said flexible tab passes an end of said protrusion, said tab
returns to an initial position while providing an audible signal indicating an end
of injection.
FURTHER ASPECTS OF THE INVENTON ARE
[0062]
- 1. A medication injection pen comprising:
a housing;
a dose set knob rotatable with respect to said housing to set a desired injection
dose;
a leadscrew provided with a thread element and advanceable in a first direction via
a corresponding thread engagement, said first direction being that which expels medication
from a cartridge;
a driver rotationally fixed to said leadscrew for preventing relative rotation therebetween,
said driver being rotatable in a first direction to rotate said leadscrew and advance
said leadscrew in said first direction;
a setback member rotationally fixed to said driver for preventing relative rotation
therebetween; and
a click element positioned between said dose set knob and said setback member, said
click element comprising a first arm member engaging an internal surface of said dose
set knob, and a second arm member engaging an external surface of said setback member,
wherein one of the said first and second arms produces an audible signal when said
dose set knob is rotated with respect to said housing.
- 2. A medication injection pen according to 1, wherein said internal surface of said
dose set knob and said external surface of said setback member each comprise a plurality
of teeth.
- 3. A medication injection pen according to 2, wherein said teeth of said dose set
knob are configured to allow relative rotation between said dose set knob and said
click element in a first direction, and said teeth of said setback member are configured
to allow relative rotation between said setback member and said click element in a
second opposite direction.
- 4. A medication injection pen according to 3, wherein when said dose set knob rotates
relative to said click element in said first direction, said first arm produces the
audible signal, and when said setback member rotates relative to said click element
in said second direction, said second arm produces the audible signal.